Septic systems and septic system components are well known in the art. Such systems are typically found in relatively sparsely populated areas not otherwise serviced by municipal waste water systems. The purpose of a septic system is to dispose of the wastewater that is generated by the occupants of a home or other building in such a manner that surrounding soils can be used to disperse the wastewater without causing an adverse effect on ground water and, in turn, on public health and the environment in general. To accomplish this task, septic systems are normally comprised of a septic tank, a distribution system and a leaching system.
The septic tank is connected to the plumbing of a home or building by means of a sewer line. The septic tank provides a holding area for the settling of waste solids and for some initial treatment of the waste. Generally, septic tanks have baffles to slow the velocity of the liquid moving through the tank and to prevent solids from leaving the tank. In this way, properly functioning septic tanks produce an effluent of fairly uniform quality.
The effluent then moves to a distribution system that directs the flow of effluent from the septic tank to the leaching system in such a manner as to fully utilize the leaching system. Most systems take advantage of gravity, meaning that flow runs through piping and distribution boxes without the assistance of any mechanical device such as a pump.
The leaching system disperses the sewage effluent over a given underground area and into the surrounding natural soils. There are several types of leaching systems and the specific type used often depends on the surrounding soil conditions. Most residential leaching systems use stone filled leaching trenches but galleries, pits, and beds have also been used.
In the experience of this inventor, private on-site wastewater treatment systems have finite lifetimes due to many factors including household water use, excessive introduction of chemicals into the waste stream, poor maintenance, and environmental factors. Replacement of any septic system component that may be required to deal with remediation of the entire system can be extremely expensive. The reason for this is the fact that the septic system components, for the most part, are buried underground as previously described and are largely inaccessible.
A very significant factor is that passive septic systems typically rely on the presence of indigenous anaerobic bacteria to break down the solid waste introduced to the system. As solid waste enters the septic tank, it flows through the series of baffles that are designed to reduce the velocity of the flow as previously described. Generally, three identifiable layers occur in a septic tank. First, as designed, solid wastes precipitate out of the flow to the bottom of the septic tank. This layer is generally known as sludge. Liquid effluent is the intermediate layer and generally consists of liquids and solids partially broken down into liquids by the anaerobic bacteria that are present in the septic tank. This intermediate layer is drained off to the absorption field. The top layer in the septic tank is generally known as the scum layer. The scum layer is comprised of mostly residual detergents, soaps, fats and oils and has a tendency to float at the top of the septic tank. Optimally, the septic tank is designed such that only the partially treated liquid effluent is permitted to leave the septic tank for the absorption field. Unfortunately, this is not always the case.
The standard septic system is passive in that it relies on the presence of indigenous anaerobic bacteria to break down the solid wastes introduced into the system. Anaerobic bacteria thrive in conditions such as those that exist at the bottom of a septic system, where oxygen is lacking. Accordingly, septic systems are designed to have the capacity to treat a certain amount of solid wastes based on the capability of the indigenous bacteria to break down the solid waste over a certain period of time. Therefore, the average amount of solid waste produced per day should be approximately equal to the amount that the anaerobic bacteria can break down in one day.
Aerobic bacteria are also indigenous and occur naturally within the waste stream. Aerobic bacteria, however, exist and function only where oxygen is present. While aerobic bacteria typically break down solid wastes more quickly than anaerobic bacteria, they are ineffective at breaking down sludge, or the solid layer at the bottom of the septic tank, because there is no oxygen present in that layer. Due to increased installation and operating costs, aerobic systems that would otherwise eliminate this sludge layer are not favored for home use.
As anaerobic bacteria digest solids suspended in the effluent as they make their way to the absorption field or in the absorption field, the suspended solids and accompanying bacteria are then deposited at the interface between the absorption field and the soil surrounding the system. This layer is known as the “bio-mat” and it performs further filtering of the effluent. Unfortunately, the bio-mat layer can grow to a thickness where it almost completely, or almost completely, impedes absorption.
While there are many ways in which septic systems can fail, two of the most likely modes of failure include the creation and thickening of a bio-mat layer at the absorption field component of the system due to the decomposition of solids within the effluent. Excess sludge and scum from the septic tank can also build up in this bio-mat. For example, when the rate of decomposition caused by the anaerobic bacteria is incapable of keeping up with rate of solids draining into the system, the septic tank fills with sludge. As the sludge level gets higher, the scum level at the top of the tank takes up more space. This causes the liquid effluent to run through the septic tank more quickly, which prevents solids from settling. The solids that fail to settle in the septic tank proceed to the absorption system, where they frequently plug the pores in the soil used for absorption. The scum layer can also find its way out of the septic tank and similarly prevents soil absorption. And if too much of the absorption field is plugged by scum and solids, the effluent will actually back up in the absorption area and cause muddy spots in the area above the absorption field. This is a sign that the absorption field has failed, an extremely malodorous and unsightly condition.
As alluded to earlier, replacement of soil absorption systems is frighteningly costly and heavily regulated by states, counties and municipalities due to the threat that malfunctioning systems pose to the groundwater. Replacement systems are very expensive, with the actual expense depending on the condition of other components in the septic system. Some owners choose to convert their existing passive system to an active system, an even more costly endeavor. Another possible option is to create an above-grade soil absorption system. Above grade systems also have operating and maintenance expenses and those are even greater than passive systems. Holding tanks are frequently the option of last resort as they are also expensive and need to be regularly pumped by a commercial contractor.
Frequently, a failing or failed soil absorption system can be remediated with the support of naturally occurring aerobic bacteria in the system. In theory, an aerobic system could eliminate or substantially reduce the failure rate of an absorption field. Unfortunately, aerobic bacteria also require the introduction of oxygen into the waste stream. Therefore, there is a need for a temporary means for introducing oxygen into a failed or failing soil absorption field for the purpose of converting the biochemical process from an anaerobic one to an aerobic one. The forced introduction of oxygen into the system would allow the aerobic bacteria to scour the bio-mat, thereby working to reduce the thickness and/or increase the permeability of the bio-mat and permit the system to revert back to an anaerobic passive system as originally designed. There is also a need to alter the biochemical process by conversion of the complete soil absorption component or a localized area of it.